The advantages of Through Glass Via (TGV) and Through Silicon Via(TSV) processes over TGV are mainly:
(1) excellent high-frequency electrical characteristics. Glass material is an insulator material, the dielectric constant is only about 1/3 of that of silicon material, and the loss factor is 2-3 orders of magnitude lower than that of silicon material, which makes the substrate loss and parasitic effects greatly reduced and ensures the integrity of the transmitted signal;
(2) large size and ultra-thin glass substrate is easy to obtain. Corning, Asahi and SCHOTT and other glass manufacturers can provide ultra-large size (>2m × 2m) and ultra-thin (<50µm) panel glass and ultra-thin flexible glass materials.
3) Low cost. Benefit from the easy access to large-size ultra-thin panel glass, and does not require the deposition of insulating layers, the production cost of glass adapter plate is only about 1/8 of the silicon-based adapter plate;
4) Simple process. There is no need to deposit an insulating layer on the substrate surface and the inner wall of the TGV, and no thinning is required in the ultra-thin adapter plate;
(5) Strong mechanical stability. Even when the thickness of the adapter plate is less than 100µm, the warpage is still small;
(6) Wide range of applications, is an emerging longitudinal interconnect technology applied in the field of wafer-level packaging, to achieve the shortest distance between the wafer-wafer, the minimum pitch of the interconnect provides a new technology path, with excellent electrical, thermal, mechanical properties, in the RF chip, high-end MEMS sensors, high-density system integration and other areas with unique advantages, is the next generation of 5G, 6G high-frequency chip 3D It is one of the first choices for 3D packaging of next-generation 5G and 6G high-frequency chips.
The molding process of TGV mainly includes sandblasting, ultrasonic drilling, wet etching, deep reactive ion etching, photosensitive etching, laser etching, laser-induced depth etching, and focusing discharge hole formation.
Recent research and development results show that the technology can prepare through holes and 5:1 blind holes with a depth to width ratio of 20:1, and have good morphology. Laser induced deep etching, which results in small surface roughness, is the most studied method at present. As shown in Figure 1, there are obvious cracks around ordinary laser drilling, while the surrounding and side walls of laser-induced deep etching are clean and smooth.
The processing process of TGV interposer is shown in Figure 2. The overall scheme is to drill holes on the glass substrate first, and then deposit barrier layer and seed layer on the side wall and surface. The barrier layer prevents the diffusion of Cu to the glass substrate, while increasing the adhesion of the two, of course, in some studies also found that the barrier layer is not necessary. Then the Cu is deposited by electroplating, then annealed, and the Cu layer is removed by CMP. Finally, the RDL rewiring layer is prepared by PVD coating lithography, and the passivation layer is formed after the glue is removed.
(a) Preparation of wafer, (b) formation of TGV, (c) double-sided electroplating – deposition of copper, (d) annealing and CMP chemical-mechanical polishing, removal of surface copper layer, (e) PVD coating and lithography, (f) placement of RDL rewiring layer, (g) degluing and Cu/Ti etching, (h) formation of passivation layer.
To sum up, glass through hole (TGV) application prospects are broad, and the current domestic market is in the rising stage, from equipment to product design and research and development growth rate is higher than the global average
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Post time: Jul-16-2024